Several devices have been proposed and at least two marketed to determine when excessive skin damaging ultraviolet B (UVB) radiation is incident on a subject. The devices are usually used to enable a subject to be apprised of excessive sun exposure during suntanning sessions or the like.
The prior art devices have generally included a UVB radiation photodetector which drives electronic circuitry. The circuitry responds to accumulated radiation incident on the detector during an exposure session. The circuitry may also be responsive to signals indicative of subject skin type and sun protection factor (SPF) of the skin. The sun protection factor is determined by UVB blocking materials, either a lotion or gel, applied to the subject's skin. If no sun protecting lotion or gel is applied to the subject's skin, the sun protection factor is one. As the blocking capability of the lotion or gel increases, the sun protection factor associated therewith increases accordingly. Typically, the skin type and sun protection factor indications are combined to derive an indication of the length of time the subject can be exposed to the skin damaging UVB radiation. In response to the accumulated skin damaging UVB radiation incident on the subject reaching a preset value determined by SPF and skin type, an indicator, which may be aural and/or visual, is activated.
The prior art devices have either been laboratory devices, not suitable for commercialization because of size and cost constraints and because of difficulty in use, or relatively expensive commercial devices. Neither attempt to commercialize has apparently been particularly successful.
The prior art devices have required the user to place the device in close proximity to his location at a position where the photodetector is constantly exposed to the source of skin damaging UVB radiation in the same manner that the skin is exposed to the UVB source. Such positioning is necessary to enable the accumulated skin damaging UVB radiation incident on the detector, and therefore on the subject, to be accumulated. Such placement of the device has obvious disadvantages, relating, for example, to the likelihood of losing the device, sand or dirt blocking the detector field of view, sand or dirt penetrating the interior of a case for the device, and mounting the device so that the intensity of the skin damaging UVB radiation incident on the photodetector is approximately the same as the intensity of the radiation incident on the subject's skin.
Some of these problems can be resolved if the detector and circuitry associated therewith are in a housing easily mounted on the body of the subject. Such a housing would conveniently be in the form of a wristwatch. A problem, however, in mounting the prior art devices on the body of the subject is that the detector for the skin damaging ultraviolet radiation is not exposed to the radiation source in the same manner that much of the skin of the subject is exposed to the radiation. Hence, the accumulated radiation on the detector is likely to be a very inaccurate indicator of the actual amount of radiation experience by the subject.
A further problem, from a commercial standpoint, in mounting an indicator for exposure time to skin damaging UVB radiation in a watch casing is that the consumer expects the cost of such an indicator to be about the same as for a sports electronic wristwatch or timepiece. Hence, the number of parts which can be added to a conventional sports, electronic wristwatch or timepiece to provide the exposure time indicator function must be minimized. Otherwise, the cost of the device will be such that there is a low likelihood of consumer acceptance. Preferably, the elapsed time indicator for skin damaging UVB radiation is combined with watch functions of a modern electronic watch, i.e., time of day, day of the month and month of the year.
It is, accordingly, an object of the present invention to provide a new and improved apparatus for and method of indicating the expiration of maximum safe elapsed exposure time of skin of a subject to damaging ultraviolet radiation.
Another object of the present invention is to provide a new and improved apparatus for and method of indicating when maximum safe elapsed exposure time to skin damaging ultraviolet radiation has expired independently of radiation accumulated on a detector for such radiation.
A further object of the present invention is to provide a device adapted to be worn on a subject, to signal to the subject that maximum safe exposure time to skin damaging ultraviolet radiation has expired, even though a detector in the device is not constantly pointed at a source of the radiation.
An additional object of the present invention is to provide a new and improved device mounted in a wristwatch type casing for indicating to a subject that maximum safe exposure time of the skin of the subject to skin damaging ultraviolet radiation has expired.
An additional object of the present invention is to provide a new and improved device that has approximately the same cost as an electronic sports wristwatch, and which provides many of the functions of an electronic sports wristwatch as well as indications of the expiration of maximum safe exposure time of skin of a subject wearing the device to skin damaging ultraviolet radiation.
An additional object of the invention is to provide a new and improved device including a detector responsive to skin damaging ultraviolet radiation connected by a minimum number of parts to a microcomputer which drives an LCD display, wherein the entire device has a cost approximating that of a conventional electronic sports watch.
Another object of the invention is to provide a new and improved apparatus for and method of indicating maximum safe elapsed exposure time of a subject to skin damaging ultraviolet radiation wherein variations in radiation intensity, sun protection factor and interruptions in exposure are accommodated.